understanding api for dummies

using object, just write an object, then anything can be solved, now do the qualification, only a part of the type can come in, if not this type or its subclass, then the direct compilation fails. Before it was compiled nothing, run out of trouble.Many of the updates in Java now are run-time errors that go to compile time, which is more secure.The generic type of the qualified knowledge point is specifically written as follows, after qualification, you can directly take the inheritance method.

One.What is a generic interface? The previous example created so many classes that it was cumbersome.The first thing to understand is that the interface is an abstract class, and after the declaration, the following class is implemented. The methods in the interface are the classes that are implemented. This combines the interfaces with generics. In the preceding chapters, you combine generics with classes, methods.A generic definition on a class is a generic class that is defined on an interfac

it on the value. If the binary tree is the following painting, take the first 28,28 in these three numbers is the smallest, the right place is full of big, then this code how to write it?No, there's no comparison here. All returns a positive number. Return 1 means this, 28 advanced come, Liasi and zhangsan a ratio, Lisi is bigger than Zhangsan, binary tree Regardless of other, see return value is positive or negative, or 0. Watching the output is the same as storing the result, which is ordered

,When importing a list package, the list has the name in different packages in Java, and the java.awt package or Java.util package has a list. If the window comes out and returns directly, the java.awt package is imported. In the continuation, the method of invocation is not seen.which element is deleted and which element is returned. Remove can change the length. In order to know more clearly, the light knows to delete a certain corner mark, but also to return let us know what the deleted eleme

that are most clearly set. Can get the length of the method, no outside length and size. If size is 0, there is no element. The IsEmpty method is true,size if there are elements, the IsEmpty is false. The collection is judged by size, but encapsulated as a isempty. The iterator method that gets the binding element is the iterator. An iterator is a method that is specifically used to remove elements from the collection.The return value of the iterator is very special, not the element being fetc

, directly printing is a large string, to take out the inside of something difficult to fetch. You can now remove any element by means of an iterator.The use of iterators, first to judge there is no, then a fetch. (now it's all part of the story)What is the other method of extraction?Iterator it is a reference that can be used by it at the end of the while. It.next (); it can not be taken, although it is not available, but it is still in use, in other words, it is in memory.As the iterator ends,

-defined tool class, the previous example can be used in a different way.The late 1.6 release also provides a number of new methods in the Linklist linked list structure. As shown in.The functions of these methods and the existing methods are the same, but there are some differences, the upgrade is for a reason.The difference needs to know which method is clearly used when developing.GetFirst method has a feature, if there is nothing in the list, call the method, there is no thing. It throws an

One.There are eight basic data types: Byte,short,int,long,float,double,char,boolean. In the world of Java, everything is object. To make it easier to manipulate the basic data type values, we encapsulate them in objects, and classes that describe the basic data types are called basic data type Object wrapper classes.There are eight basic data types, which means there are eight wrapper classes.The class name has a first-character capitalization feature, originally Byte,short,int ... Lowercase are

only three methods in the iteration, one to judge, one to get, the last to delete, and no method to add. The iterator itself has limitations, and the iterator below has sub-interfaces, Listiterator list iterators.The sub-interface provides added methods, modifications, fetches, deletions, and judgments. How do I get a sub-interface object? There is another method in the list collection that is not described, that is, Listiterator (), which can be used to get a list iterator. This iterator, only

, so it's a member.Why do you have to define it inside and put it on the outside? Myentry is a content that contains keys and values, is a mapping of key and value objects, and there is only one existing map map that has a relationship. Instead, it encapsulates the relationship as an object, and the relationship accesses the keys and values in the map. That is, there are internal rules in the external rules, and internal rules directly access the contents of the external rules. What dot, all are

very useful oh.NgclickThe Ngclick directive allows a specified expression to be executed when an element is clicked.Format: ng-click= "value"Value: An expressionUsing code:{{count}}Mouse click event, do not say more.NgdblclickThe Ngdblclick directive allows you to execute a specified expression on an DblClick event.Format: ng-dblclick= "value"Value: An expressionUsing code:{{count}}Double-click the mouse event without explanation.After summing up, early to bed and early to good health, the beas

. The advantage is that object appears, improve extensibility, but with the drawbacks, is to strong turn. Not strong turn can not be used.Now make some changes to the tool loaded with object in the program, make a change.Write the changes back and forth in a Java tool class, looking up and down. When writing a tool class, this is used to manipulate the object tool class, followed by which object you want to manipulate, not sure. It used to be an object, and now it has a generic type. Manipulate

One.For a parse of the string memory.Now introduce a method, for a while to use, but the actual development is not uncommon.Intern () can operate on a constant pool,S1 is an object, and then uses the S1 object to invoke the method in the operation constant pool, calling this method to return the object in the pool.And then the comparison, S1==s2? The result is false, and it is one thing to follow the same notation.Here the S1 is an object in the heap, I object to the pool to find, not in the poo

One.Focus on the ArrayList and LinkedList query the reasons for the speed, both additions and deletions have been introduced.The array is a contiguous space, placed in the heap memory, and the elements are placed inside the array.Explain why queries for arrays are fast (all relative) and why the list queries are slow.In heap memory, much of the data is randomly placed, but if a part is stored as an array, it is stored in a corner label. Querying on successive sections is faster than searching in

greater nor less than, is equal to. Then the two elements are the same, the same object, so the Zhouqi is canceled.Some people say that the judgment is one step less, and when the age is judged the same, the name should be judged again.Note that when we write this comparison, we usually rely on the conditions are not unique, called there may be the main conditions at the same time, there are secondary conditions. It is called if the primary condition is the same, continue the comparison on a se

algorithm, and also overrides the Equals method in object, and defines whether the content of its own judgment is the same.Let's take a look at how it's done. Open the source string, outline on the left is the Outline window, which lists all the members of the current class, so it is more convenient to find.Find Hashcode, which shows the string hash algorithm. How it counts, no matter what, it's based on the character of the string itself.The value here is actually the array corresponding to th